Field of the Invention
The present invention relates to an electrostatic image developing toner. More specifically, the present invention relates to an electrostatic image developing toner excellent in low-temperature fixing property and low glossiness.
Description of the Related Art
For the purpose of coping with a faster speed of printing, expansion of paper types, or reduction of environmental impact in recent years, it has been required to reduce heat energy consumed in the fixing process of toner image. In order to reduce the heat demand in the fixing process of toner image, there has been a need for improving low-temperature fixing property of an electrostatic image developing toner (also simply referred to as “toner”, hereinafter). One known method of achieving the purpose is to use, as a binder resin, a crystalline resin such as crystalline polyester characterized by its sharp melting performance.
For example, JP-A-2006-251564 proposes an electrostatic image developing toner which contains a binder resin in which a crystalline polyester resin and an amorphous resin are mixed. By using the crystalline polyester resin and the amorphous resin in a mixed manner, the fixing temperature may be lowered, since the crystalline moiety melts when the toner is heated during fixing above the melting point of the crystalline polyester resin, and thereby the crystalline polyester resin and the amorphous resin become dissolved to each other. This sort of toner has, however, been suffering from an excessive glossiness of image and glare, since the crystalline polyester resin and the amorphous resin fuse with each other during fixation under heating to cause a sharp fall in melt viscosity of the resin as a whole.
A possible method of suppressing such excessive increase in the glossiness is to allow the crystalline polyester and a high-softening-point vinyl resin to form a domain phase in an amorphous resin used as a matrix. According to the description, the high-softening point vinyl resin starts to melt into the matrix when kept at high temperatures during fixation under heating, so that the matrix reduces the viscosity only slowly, the glossiness may therefore be suppressed from excessive increase, and thereby the glossiness may be stabilized on a variety of paper types.
Even such toner has, however, not been still enough to suppress the excessive increase in glossiness, making the resultant image highly glossy, and making a character image less readable due to glare. The toner is still insufficient regarding recent requirements for lower fixing temperature for coping with higher printing speed, and a wider variety of paper types (including printing on coated paper).
In short, it has been difficult to properly balance the low-temperature fixing property with the property allowing formation of low-gloss image (low glossiness), leaving the toner still on the way to acquire a sufficiently low glossiness.